[osg-users] 3D Texture Compression

[hesicong2006]

Hi everyone,
I have a volume data which is 256*256*256 cube, and I found it very slow 
when ray-casting. And I notice the video memory usage is 74M. I want to 
compress it to an hardware-support compressed format (S3TC_DXT1 or 
S3TC_DXT3 or S3TC_DXT5), but I found no example demonstrate how to use 
it. I tried to use 
osg::Texture3D::setInternalFormatMode(osg::Texture::InternalFormatMode::USE_S3TC_DXT1_COMPRESSION), 
but the video memory usage appears same as before.
My computer has a Nvidia Geforce 8800 with latest driver, 3D compress 
texture is support by this hardware.
Could anyone tell me if another steps needed to use 3D texture compress? 
Thanks.